5-Million-Year-Old Arctic Fox Ancestor Found in Tibet

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The fossilized jawbone and teeth of a 5-million-year-old fox have
been unearthed in Tibet.

The fox, Vulpes qiuzhudingi, is probably the ancestor of
modern Arctic foxes. The discovery, along with several other
fossils from cold-loving mammals, buttress the Out
of Tibet hypothesis: That iconic ice-age mammals such as
woolly mammoths, saber-toothed tigers and giant sloths first
evolved for the cold weather in Tibet before fanning out over the
steppes of Central Asia and into North America.

Out of Tibet

Several years ago, paleontologists excavating the Zanda Basin in
Tibet unearthed a 3.7-million-year-old
woolly rhino fossil that not only was older than all other
fossils of the species, but also was found much farther south
than those prior specimens. At that time, the Arctic was
much warmer than it is today, whereas the snowy, high Tibetan
plateau was just a touch warmer, said study co-author Zhijie Jack
Tseng, a paleontologist at the American Museum of Natural History
in New York. [ High
& Dry: Images of the Himalayas and the Tibetan Plateau ]

That led the researchers to propose that the frigid,
high-altitude climate of Tibet was a staging ground where many of
the shaggy-coated, cold-loving megafauna first adapted to the
cold. When Earth's temperatures plunged at the onset of the last
ice age about 2.6 million years ago, these cold-loving creatures
emerged from the Tibetan plateau to colonize most of the Arctic
and colder portions of North America.

Living relative

In 2006, the researchers also found a single tooth in the Zanda
Basin, but couldn't match it to a specific animal species. Over
the next several years, they went on to find two other fossils
that revealed the lower jaw and some of the teeth from ancient
predatory foxes, allowing
them to identify the original tooth as well.

The fox fossils ranged from 3.6 million to 5 million years old,
and the teeth looked a lot like those of the modern Arctic fox,
which now lives across the Arctic, from Scandinavia and Russia in
the west all the way to Greenland and Iceland.

"The arrangement of the cusps on the tooth are more or less in a
straight line and pretty sharp," Tseng told Live Science. "That
meant that the fox was using that tooth for cutting and shearing
meat," just as the Arctic fox does today.

The discovery marks the first time that an older predecessor to a
modern Arctic creature has been found in Tibet, buttressing the
Out of Tibet hypothesis, Tseng said.

The team has also found other fossils from archaic, cold-adapted
mammals throughout Tibet, such as ancient
snow leopards, wolf-sized dogs and hyenas. And, just like
modern Arctic species that must subsist mainly on meat during the
long, frosty winter months when plant-based food is almost
nonexistent, these ancient animals were more carnivorous than
similar animals that live in more temperate climates, Tseng said.

The findings were published Tuesday (June 10) in the journal
Proceedings of the Royal Society B.